- 4608 - MOON - how far away? - This may seem like a question with a simple answer: How far away is the moon? But the distance between Earth and our closest neighbor is not a single number. The commonly quoted average distance of 384,400 kilometers, or 238,855 miles, is a good approximation. However, the moon's orbit around the Earth is elliptical, so its distance from Earth varies.
--------------------------------------------- 4608
- MOON - how
far away?
-
- That distance ranges from roughly 221,500
miles (356,470 km) away at its closest point to Earth, called perigee, to
252,000 miles (405,600 km) away at its farthest point, called apogee.
-
- The distance at apogee is so great, the
solar system's seven other planets (Mercury, Venus, Mars, Jupiter, Saturn,
Uranus and Neptune) could fit between Earth and the moon. This thought
experiment works if the average diameters of the planets are added together,
which equals 236,100 miles (380,016 km).
-
- We can thank the Apollo astronauts for the
accuracy of these measurements. Using
reflectors left on the lunar surface in the 1960s and '70s, scientists today
can shine high-powered lasers at the moon and measure their reflection speed to
determine the satellite's distance from Earth.
-
- The moon shines 30% brighter, and appears
14% larger in diameter, during perigee than when it's at apogee. These changes are sometimes referred to as
a 'supermoon' when the Moon is closest and as a 'micromoon' when it is furthest
away. Both the moon's distance and its phases follow the same roughly 27-day
lunar cycle, they are not directly related.
-
- The fourth and final "supermoon"
of 2024 will be 100% illuminated on Friday, November 15, 2024,
but the best time to see it from North America will be as it rises in
the east on Novemver 16.
-
- November's full moon is typically called the
“Beaver Moon” for the beavers that typically build their winter dams this time
of year in the northeastern U.S. It's also called the Frost Moon and the Snow
Moon in North America because the continent is on the verge of winter and the
colder temperatures that come with it.
-
- This year's Beaver Moon is the final of
four supermoons in 2024, following August's Sturgeon Moon, September's Harvest
Moon and October's Hunter's Moon. A supermoon is a consequence of the moon's
elliptical orbit, which means the moon reaches its closest point to Earth,
known as perigee, at a slightly different time every month. When a full moon
comes within 90% of perigee, it's a supermoon.
-
- A full moon is best observed as it rises in
the east in early twilight, shortly after the sun has set in the west. That
doesn't quite happen on Nov. 15 in North America, where the full moon rises
significantly before sunset. So the best time to see the supermoon will be at
moonrise on Saturday (Nov. 16), which will be about 20 to 30 minutes after
sunset across the continent.
-
- If you look at the Beaver Moon on the night
of Nov. 15, the sparkling Pleiades open star cluster, also known as the
"Seven Sisters," will be to its lower left. On Nov. 16, the Pleiades
will be to the moon's upper right.
-
- In most cases, the average distance between
Earth and the moon is accurate enough for the general public. However, some
cases such as planning a mission to orbit or land a spacecraft on the moon,
require a more precise measurement. Luckily for lunar researchers, these
considerations are much less daunting than for missions to Mars, which has a
distance variation of 35 million miles compared with the moon's roughly 31,000
miles.
-
- The variation in distance between perigee
and apogee can affect travel time by a small margin. But, other factors, like
trajectory, landing site conditions, and solar illumination, tend to be more
important considerations for Moon missions.
-
- Early in lunar history the Moon was much
closer but it has been slowly drifting from the Earth for over 4 billion
years. We're fortunate to be around at
this time where the Moon is at its current range in distances since we can get
those magical moments where the Moon blocks the Sun and we get total solar
eclipses.
-
- The largest and oldest-known impact site on
the moon is the South Pole-Aitken basin. Scientists have dated the basin to the
period between 4.32 and 4.33 billion years ago. For billions of years, our celestial
neighbor has been absolutely bombarded by asteroids and comets, and the assault
has left behind a heavily pockmarked lunar surface.
-
- A research team led by scientists at the
University of Manchester determined the age of the basin by analyzing a lunar
meteorite known as Northwest Africa 2995. The meteorite, which was found in
Algeria in 2005, contained uranium and lead that was dated to this period.
-
- For several decades there has been general
agreement that the most intense period of impact bombardment was concentrated
between 4.2–3.8 billion years ago, in the first half a billion years of the
moon's history. But now, constraining
the age of the South-Pole Aitken basin to 120 million years earlier weakens the
argument for this narrow period of impact bombardment on the moon and instead
indicates there was a more gradual process of impacts over a longer period.
-
- This has implications for Earth's early
history, too. We know that the Earth
and the Moon likely experienced similar impacts during their early history, but
rock records from the Earth have been lost.
We can use what we have learnt about the moon to provide us with clues
about the conditions on Earth during the same period of time.
-
-
November 14, 2024 4608 -
MOON - how far away? 4608
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--------------------- --- Friday, November 15,
2024
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